(1) Field of the Invention
This invention relates to a novel coliform bacillus, Escherichia coli (hereinafter referred to as E. coli), having a gene for staphylokinase production (hereinafter referred to as "SAK gene") and to a process for the production of staphylokinase by use of the novel microbe.
(2) Description of the Prior Art
Staphylokinase (hereinafter referred to as SAK) is a fibrinolytic enzyme which is produced by Staphylococcus aureus (hereinafter referred to as S. aureus).
The function of SAK is to transform plasminogen in blood into plasmin, which in turn acts on fibrin to lyse the same. There are known, as enzymes of similar activity, urokinase which is present in human urine and streptokinase which is produced by streptococci. All these enzymes find use in medicine as fibrinolytics, for example, anticoagulants (blood coagulation inhibitors) and antithrombotics. In view of such usefulness, many attempts have been made to improve processes for the production, extraction and purification of these enzymes.
It is known that capability for producing SAK is a trait imparted to a S. aureus host by way of what is called lysogenic conversion, i.e., lysogenization of the host with a temperate phage. Accordingly, prior art processes for the production of SAK comprise selecting from strains of S. aureus a strain having SAK producibility, or lysogenizing a S. aureus strain incapable of SAK production with a phage capable of lysogenic conversion of SAK, culturing, in either case, the obtained strain and obtaining SAK from the culture.
S. aureus is, however, a pathogenic bacterium and so cautious consideration is required in the handling thereof. Therefore, prior art processes are not particularly suited for SAK production on an industrial scale. Moreover, in order to achieve high yields of SAK, it is necessary to carry out cultivation for a long period of time. In this regard, also, the prior art processes have drawbacks for SAK production on an industrial scale.